1. Field of the Invention
The present invention relates generally to label-switch path communications networks, and more specifically to alternate routing of packets in the event of a failure on a working label-switched path.
2. Description of the Related Art
Many alternate routing methods have hitherto been developed as a solution in the event of a network failure. In an Ethernet network, messages are exchanged between switches to autonomously find alternate routes at different locations of the network. MPLS (Multi-Protocol Label Switch) is known as a traffic engineering technique using label-switched paths. Also known in the art as a high-speed alternate routing technique is the path protection technique extensively used in SDH (Synchronous Digital Hierarchy) networks. A “Resilient Packet Ring” network is standardized by the IEEE 802.17 working group. In a RPR network, “steering” and “wrapping” techniques are used in the event of a ring failure. With “steering”, the ring “steers” at a source node to recover the failure from the starting point of the affected link. With the “wrapping” technique, the ring “wraps” (doubles back on itself) around the point of failure to form a single contiguous ring.
With the known spanning tree algorithm, routes are autonomously are determined by nodes. As such, management of alternate routes in advance of a network failure is impossible. Alternate routes, which may possibly be taken in the event of a failure, cannot be established on a policy base. Additionally, a substantial amount of time is taken to determine the alternate routes. With MPLS where the alternate routing is determined by the label value, the software-based label processing results in a long path switching time in comparison with the wrapping (or loopback) and path protection techniques. Since the RPR technology can only be used in ring network applications, this technology cannot be applied to Ethernet applications.
In addition, the use of the VLAN (Virtual LAN) tag of Ethernet network as a path-identifying label allows paths to be merged or branched out. However, when a given path is branched out to an alternate path, the communication disadvantageously switches to a broadcast mode until the system learns MAC addresses.